Recently, as the lack of an energy resource such as petroleum or coal is expected, the interest in the substitute energy has been more increased. In this regard, a solar cell converting solar energy into electric energy is spotlighted.
A solar cell (or photovoltaic cell) is a core element in solar power generation to directly convert solar light into electricity.
For example, if the solar light having energy greater than bandgap energy of a semi-conductor is incident into a solar cell having the PN junction structure, electron-hole pairs are generated. As electrons and holes are collected into an N layer and a P layer, respectively, due to the electric field formed in a PN junction part, photovoltage is generated between the N and P layers. In this case, if a load is connected to electrodes provided at both ends of the solar cell, current flows through the solar cell.
Current generated from the solar cell is transferred to a junction box through a bus bar. In general, when the bus bar formed at a top surface of a solar cell panel is connected to the junction box formed at a bottom surface of a lower substrate, the bus bar may be partially exposed to the outside so that the reliability may be reduced.
When the junction box is formed at the bottom surface of the lower substrate, because a junction area between the lower substrate and the junction box is not wide, the lower substrate and the junction box may be separated from each other due to external pressure so that it is necessary to reinforce a bonding strength between the lower substrate and the junction box.